ExpressJS static dynamically

I'd like to serve /mbti/:lang/ with static files from directory ./mbti/:lang/.

That is:

/mbti/en/ -> ./mbti/en/index.html
/mbti/en/some.json -> ./mbti/en/some.json

I found static, but seems like it can't do this:

app.use('/mbti/:lang/', express.static(__dirname + '/mbti/' + :lang));

How can I implement this? thanks.

You shouldn't need to do that, just make /mbti/ a static route and anything below that root will be served as static

express.static(__dirname + '/mbti');